Even some of the most prominent mutual-fund firms outsource some funds' management. Researching these third-party offerings takes a little legwork, but investors may be rewarded.

The manager of the $6.7 billion Harbor Bond fund isn't an employee of Chicago-based Harbor Capital Advisors. He sits in an office 2,000 miles away, helping oversee a different asset-management firm. Yet, since 1987, Pimco co-founder Bill Gross has run the fund [ticker: HABDX] on behalf of Harbor. While Pimco...